Controlling of tension in running threads



June 11, 1963 A. HEZZLEWOOD 3,093,282

CONTROLLING 0F TENSION IN RUNNING THREADS Filed Oct. 51. 1960 2 Sheets-Sheet 1 June 11, 1963 A. HEZZLEWOQD 3,093,282

CONTROLLING OF TENSION IN RUNNING THREADS Filed Oct. 51. 1960 r 2 Sheets-Sheet 2 Inventor /44 4/1 #52245 W000 Home I 3,093,282 w Patented June 11, 1963 fiice 3,093,282 CONTROLLING F TENSION IN RUNNING THREADS Alan Hezzlewood, Usk, England, assignor to British Nylon Spinners Limited, Pontypool, England Filed Oct. 31, 1960, Ser. No. 66,133 Claims priority, application Great Britain Nov. 12, 1959 6 Claims. (Cl. 2267) The present invention concerns improvements in or relating to the controlling of tension in running threads, and has particular reference to the elimination, or virtual elimination, of tension therein.

The effect of fluctuations in the tension of a running thread used as a supply in textile operations, such as warping, weaving and knitting, leads to irregularities in the product made in that operation, which irregularities in the case of fabrics are often sutficiently obvious to lead to their rejection. Tensioning devices of the simpler varieties such as are used in by far the greater proportion of all textile operations, are useful in imposing a moderately uniform output tension therefrom; but, unless the more complicated and expensive varieties of device, having provision for compensating for variations in input tension, are utilized, the fact is that variations in the input tension of the thread will be exaggerated by the tensioning device, and hence will cause defects in, say, fabrics which may lead to their rejection.

Variations in input tension, i.e. the tension in a thread immediately prior to its arrival at a textile instrumentality, if no tensioning device is utilized, or at a tensioning device fitted to act on the thread prior to its arrival at a textile instrumentality, such as knitting machine needle, are normally present due to variations in tension resulting from the action of take-01f from the thread supply package and from variations in the tension of winding-on. Whereas steps to try and eliminate such variations are always being taken, the critical nature of tension faults in some fabrics, such as circular-knit fine nylon stockings, makes it very difiicult to eliminate the variations to below the significant level especially when take-off from the supply package is over one end thereof, as is the normal procedure on a circular knitting machine. Hence, the problem is a very real one, particularly in the case of the critical processes alluded to above; and efforts to solve it with known tensioning devices have not been altogether successful, even when devices have been used which aim to compensate for variations in input tension.

We have now approached the problem from a dinerent aspect altogether; and according to the invention we provide specific means for eliminating, or virtually eliminating, all tension in a running thread, and then either utilizing the ten'sionless thread directly as in a laboratory testing process or in a textile process, such as knitting, or passing it through a tensioning device before utilizing it in a testing or textile process in those cases where a positive feed tension is required. The fact that the thread is virtually tensionless means that a tensioning device of the additive type, such as the double-disc tensioner, can be used in this latter instance without fear of the output tension being caused to fluctuate because of variations in the input tension. Furthermore, the passing of the tensionless thread through guides will not lead to the tension multiplying effects that are normally found and such do not therefore have to be so closely guarded against as heretofore.

The invention comprises a process for reducing or eliminating the tension of a running thread wherein the thread is passed in contact with a portion of the periphery of a roller that is rotatably driven at a peripheral speed greater than the linear speed of travel of the thread in contact therewith and wherein an air flow is created having at least a component of motion in the direction of travel of the thread as it leaves the said roller and acting on the thread at, or closely adjacent to, the point whence the thread departs from the said roller and having at most no substantial component of motion in that direction which is inwardly radial of the roller at the point whence the-thread departs from the said roller.

The invention also comprises apparatus for reducing or eliminating the tension of a running thread, comprising a driven roller, around a portion of whose periphery the thread is passed, and means acting in combination with the roller for creating an air flow having at least a component of motion in the derection of travel of the thread at, or closely adjacent to, the point whence the thread departs from the said roller and having at most no substantial component of motion in that direction which is inwardly radial of the roller at the point whence the thread departs from the said roller.

In one convenient embodiment of the invention, the roller itself serves to create the air flow. Due to its rotation, and to the frictional characteristics of its surface, the roller will carry around with it a body of air. It is possible, by positioning guide vanes, or shields, around that part of the periphery of the roller with which the thread makes contact and extending away from the roller to form a diverging space around the thread as it leaves the roller, to channel the thus-created air-flow into the general direction of travel of the thread as it leaves the roller. 1

Alternatively, in another embodiment of the invention, the air flow may be created by means extraneous to the roller, as by a simple jet connected to a supply of compressed air, or by an air turbine operating within a casing, part of which is cut away and shaped so as to channel the air flow in a direction that enables it to assist in helping the thread to quit the roller, as must occur also with the construction embodying the compressed air jet.

The two vital components of the invention, namely the rapidly-rotating roller and the air flow, act together in such a way that the output tension in the yarn is reduced compared with the input tension and reduced to a steady infinitesimally small quantity whatever the variations in input tension within the ordinary range, and the thread is assisted to depart from the periphery of the roller at the appropriate point. a

The effect of the peripheral speed of the roller being greater than (say, of the order of 50% greater) the linear speed of the thread is to apply negative friction to the thread in a direction contrary to its travel. Thus, compared with the cases when the rollers peripheral speed is zero or any speed lower than that of the thread, or when it is equal to thatof the thread, in which cases, respectively, the roller serves to multiply or to add to the input tension in the thread, the roller in the process of the invention serves to subtract from the input tension.

The air flow must be in such a direction relative to the direction of travel of the thread as it leaves the roller in conditions of normal operation, that the air will assist in the departure of the thread from the periphery of the roller. Thus it should always act in a direction adapted to prevent the thread from becoming wrapped around the periphery of the roller with a greater angle than the normal one; and such correct action will occur even when the air flow, although slightly diverging, is in the same general direction as that of the thread leaving the roller.

The combination of apparatus in the process of the invention acts as a servwmechanism, in that variations in input tension will automatically be compensated for, and a uniform zero or infinitesimally small output tension be maintained, by corresponding variations in the angle through which the thread wraps in contact with the periphery of the roller. This is so, because an increase in input tension will bring about an increase in the wrap angle, such that the negative frictional effect of the roller is increased by an amount suflicient to reduce the increased tension to around zero 'at the point of departure of the thread from the'roller.

The invention will now be described with reference to the accompanying drawings, in which:

FIGURE 1 is a side elevation of apparatus according to the aforesaid convenient embodiment;

FIGURE 2 is a section through II'-II of FIGURE 1;

FIGURE 3 is a side elevation of apparatus according to another embodiment; and

FIGURE 4 is a section through IV-IV ofFIGURE 3.

The convenient embodiment illustrated in FIGURES 1 and 2 will first be described. Yam 1, such as nylon 15 denier monofilarnent, from a source not shown, such as a supply package, is led tothe tension eliminator of the embodiment, shown generally at 3, the means for imparting linear movement to the yarn also not being shown but consisting, say, of some'feed mechanism acting on the yarn after its travel through the tension eliminator.

The yarn is passed via guide pins 4, with a wrapping arc of some 120, around aluminium roller 5 mounted on shaft 6 which is driven by electric motor 7 with a peripheral speed 60% higher than the linear speed of the yarn in contact with it. The yarn in the tension eliminator is enclosed between a black Perspex (registered trademark) back plate 9 and a plain Perspex front plate or window 11, hinged at 13. Motor 7 is housed within 'a casing 15, and is supplied with power through cable 17. Vane, or shield,19 is shaped and positioned close to and surrounding roller 5 for the portion of the periphery with which the yarn is in contact, and then to extend to the yarn-departure end of the tension eliminator. Vane, or shield 21 extends from adjacent the roller 5 to the yarn-departure end of the tension eliminator, and together with vane 19 forms a space, the top and bottom boundaries of which diverge at an angle of 17 /2, within which the yarn travels from the roller out of the tension eliminator. At its closest, vane 19 is only ,4 inch away from roller 5, this forming a partial annular space; and the rotation of the roller is such as to causeair from this space to be expelled as an air flow 23, shown by the arrows, travelling in the same general direction as the yarn away from the roller. The tension in the yarn after it has left the roller will be maintained at substantially zero.

In the embodiment illustrated in FIGURES 3 and 4, yarn 1 is led into the tension eliminator 3 through guide 25. It is then passed via chrome wire guide 27, around a portion of the periphery of roller 5 which is mounted on shaft 6 and driven by electric motor 7 at a peripheral speed some 25% greater than the linear speed of the yarn, which may he, say, 500 feet per minute. Impeller, or air turbine, 29, is driven by means of a belt'31 and pulley 33 directly from theshaft 6. The impeller, or turbine, 29 has curved blades 35; and it has a casing 37 so shaped and positioned around the turbine that air is forced out in air flow 23, shown by the arrows, travelling in a direction tending to prevent further wrapping of the yarn around roller 5. Yarn 1 is led out of the tension eliminator around guide 39; and, as in the case of the other embodiment, the yarn in the tension eliminator is protected in a space of about inch depth, between a black Perspex back plate, 9, and a plain Perspex window 11, hinged at 13. Electric motor 7 is housed within'a casing 15, and is supplied with power by cable 17. Again, the tension in the yarn between roller 5 and the guide 39 is substantially zero.

It is sometimes desirable, according to'any of the embodiments of the invention that the thread on departure from the rapidly-rotating roller, should be allowed to form a free-loop, extending either upwardly, downwardly or sideways, the advantage of which is that the correctness or otherwise of the settings of the roller speed and of the air flow will be immediately apparent to an operator.

A critical function of the air flow arrangements in those processes in which the utilization of thread is only intermittent, such as a circular-knitting process, is to create the necessary conditions that will prevent the thread from being continuously forwarded by the device after utilization thereof has ceased. In the embodiments described, this function will be performed satisfactorily, in the case of the embodiment described with reference to 'FIGURES 1 and 2 by reason of the back pressure caused along the thread as it builds-up in folds between the slightly diverging vanes, immediately after utilization has ceased, leading to the contact between the thread and the roller becoming so light as to allow slippage to occur, and in the case of the embodiment described with reference to FIGURES 3 and 4 by reason of the air flow causing a slight increase in the size of the loop of thread that has just left the roller, this having the same eetfct as in the other case on the contact between the thread and the roller. It is, of course, possible to have separate interlock means that will automatically remove the thread from contact with the roller on the ceasing of utilization and that will automatically direct it back in contact with the roller on the re-starting of utilization, but such means are not to be preferred owing to their added complication to the device as a whole. It is, however, sometimes essential to have such means, as when the peripheral surface of the roller has a very high coefficient of friction with the thread, for example when it is composed of rubber.

The nature of the peripheral surface of the roller is, in fact, a matter of prime importance in the operation of the invention, and it must be selected with a view to allowing the device to cope with the range of tension variations that can be expected to be present in the thread supplied to it. For example, a rubber surface is capable of eliminating tension in a supply thread having tension variations in it of a size, in grams, up to the breaking load of the yarn, which is, of course, the maximum capability required. Such maximum capability is not often required, however, owing to thegenerally lower order of tension variations that are met with in practice; and consequently, metal surfaces, whether smooth or matt, are normally quite satisfactory, and do not have the complication that rubber surfaces introduce when utilization of thread is only intermittent.

One particularly advantageous use of the invention is in connection with the knitting of the panel yarns of a circular-knit stocking, where minor variations in takeoff tension from a double-taper bobbin of low-twist nylon monofilament yarn, which ordinarily may result in tension rings visible in the knitted stocking, are eliminated if apparatus according to the invention is fitted on the knitting machine in a position allowing the yarn to be drawn through it soon after leaving the bobbin.

What I claim is:

1. A process for reducing the tension of a running thread which comprises? contacting said running thread with an arcuate portion only of the periphery of a roller; rotating said roller at a peripheral speed greater than the maximum linear speed of the thread in contact therewith; and directing a steady flow of air tangential to said periphery at the point thereon at which the thread departs from said roller and in the direction of departure of said thread, the directing of said flow of air including the step of at least partially enclosing said portion of said roller' to form a partial annular space containing said running thread whereby rotation of said roller creates said flow of air due to friction between air in said partial annular space and the surface of said roller.

2. Apparatus for reducing the tension of a running thread comprising: a driven roller adapted to receive the running thread around an arcuate portion of the periphery; and means acting in combination with said roller for creating a steady flow of air whose direction of flow is tangential to said periphery at the point thereon at which the thread departs from said roller and is in the direction of departure of said thread, said means including a curved vane positioned close to and partially surrounding said roller whereby a partial annular space is formed around said roller and whereby friction between the surface of said roller and air in said partial annular space creates said flow of air.

3. Apparatus according to claim 2 wherein slightly diverging vanes positioned between front and back plates enclose the thread-line from the point of departure of the thread from the roller.

4. Apparatus according to claim 2 wherein the peripheral surface of the roller is of metal.

5. Apparatus according to claim 4 wherein the metal surface is a smooth surface.

6. Apparatus according to claim 2 wherein the peripheral surface of the roller is of rubber.

References Cited in the file of this patent UNITED STATES PATENTS Knebusch et a1. Sept. 26, Lamesch Sept. 9, McDermott Aug. 17, Sti'bbe et a1. Jan. 2, Schoonenberger et al. Dec. 18, Waugh Oct. 27, Newton Sept. 13, Meinshausen Oct. 11,

FOREIGN PATENTS Sweden Mar. 23, Great Britain Jan. 2, France July 15, Great Britain July 5, 

1. A PROCESS FOR REDUCING THE TENSION OF A RUNNING THREAD WHICH COMPRISES: CONTACTING SAID RUNNING THREAD WITH AN ARCUATE PORTION ONLY OF THE PERIPHERY OF A ROLLER; ROTATING SAID ROLLER AT A PERIPHERAL SPEED GREATER THAN THE MAXIMUM LINEAR SPEED OF THE THREAD IN CONTACT THEREWITH; AND DIRECTING A STEADY FLOW OF AIR TANGENTIAL TO SAID PERIPHERY AT THE POINT THEREON AT WHICH THE THREAD DEPARTS FROM SAID ROLLER AND IN THE DIRECTION OF DEPARTURE OF SAID THREAD, THE DIRECTING OF SAID FLOW OF AIR INCLUDING THE STEP OF AT LEAST PARTIALLY ENCLOSING SAID PORTION OF SAID ROLLER TO FORM A PARTIAL ANNULAR SPACE CONTAINING SAID RUNNING THREAD WHEREBY ROTATION OF SAID ROLLER CREATES SAID FLOW OF AIR DUE TO FRICTION BETWEEN AIR IN SAID PARTIAL ANNULAR SPACE AND THE SURFACE OF SAID ROLLER. 